1. Field of the Invention
The present invention relates to a digital camera that takes a photograph by forming an image of an object on a solid imaging device.
2. Description of the Related Art
Because of the reduced size and costs of their unit light receiving elements, digital cameras have recently been popular which take a photograph by forming an image of an object on a solid imaging device composed of a set of a plurality of two-dimensionally arranged unit light receiving elements to obtain image data representing this object. These digital cameras control exposure according to sensitivity set by, for example, selecting an ISO (International Organization for Standardization) value from a menu display.
If a high sensitivity is set, some of these digital cameras actualize this high sensitivity by increasing the time for which charges remain stored in the solid imaging device (for example, refer to Japanese Patent Laid-Open No. 6-165048). Other digital cameras actualize this high sensitivity by carrying out pixel mixture in which a plurality of pieces of luminance information obtained from a plurality of unit light receiving elements are integrated together so that one new piece of luminance information is formed of every predetermined number of pieces of luminance information obtained from a predetermined number of adjacent unit light receiving elements. It is assumed that in the digital camera actualizing a high sensitivity through this pixel mixture, for example, the charged coupled device is composed of 6,000,000 unit light receiving elements, i.e. recordable image size is 6 mega-pixels. Then, when high-sensitivity photographing corresponding to ISO 800 is specified, four unit light receiving elements are integrated together into one unit light receiving element. Thus, the recordable image size becomes 1.5 mega-pixels.
However, a large number of users are unfamiliar with such correlationship between the sensitivity setting and the recordable image size. Accordingly, for example, with a digital camera having a recordable image size of 6 mega-pixels, when a high sensitivity is set if an image is to be recorded so as to have an image size of 3 mega-pixels, the recordable image size becomes 1.5 mega-pixels. Consequently, a photographing process is not executed with the set recording image size (3 mega-pixels). As a result, the image quality of the resulting photograph is disadvantageously lower than intended.